The present invention relates to a template for facilitating the drilling of subsea oil and gas wells. More particularly, the present invention relates to a light-weight, cost-effective, modular design for such a template that can more easily be installed and leveled.
The drilling template of the present invention was specifically designed for utilization in commercializing a field in the Gulf of Mexico off the Louisiana coast in approximately 1800 feet (550 m) of water. Soundings of the ocean floor targeted for template supporting a conventional drilling template. This suggested a light weight configuration might be in order. On the otherhand, placement in water depths of 1800 feet, necessitates a design with sufficient strength to avoid collapsing under the hydraulic pressure exerted by the ocean. Therefore, weight reduction could not be made without regard to strength requirements.
The template design of the present invention affords both a light-weight solution and a configuration having sufficient strength to survive the rigors of the environment at a 1800 foot water depth. A frame is constructed of tubular steel members that are reinforced with ring stiffeners. The frame defines a number of (in the specific embodiment shown, six) pod-receiving openings. Well pods, that may be installed as necessary to enable the drilling to proceed, are secured into the individual openings and, preferably, provide cylindrical guides for drilling a plurality of (in the specific embodiment depicted, four) wells.
The light-weight template frame is equipped with a plurality of buoyancy tanks (at least some of which are floodable and one, removable) to enable the template to float at the field site so that it may be rigged for placement on the ocean floor. The floodable tanks may then be ballasted to the weight desired by controling valved flood ports, for floor installation. Cathodic protection is provided in the form of sacrificial anodes mounted at spaced locations along the tubular frame. The pile sleeves of the frame are provided with conventional slips to grip the pin piles that are used to secure the template to the seafloor. By engaging the template near its lowest corner and lifting, a rough level for the template (which is roughly 50 feet by 80 feet by 20 feet at its tallest end) can be obtained.
The individual well pods can be inserted in the openings and are secured in place by engagement of a plurality of latch mechanisms in a like plurality of latch-engaging receptacles. A fine tune adjustment of the level of the individual pods can be made by adjustment of gimbaled jack mechanisms associated with each of the latches.
The modular template has several advantages over conventional one piece designs. The weight reduction to facilitate leveling has already been mentioned. Another is cost avoidance or, at least, cost postponement, since subsequent will pods need only be added as successful drilling indicates installation to be warranted. Yet, another is that a pod that is damaged may be retrieved and repaired or replaced before drilling commences. In a conventional template design, no such flexibility is afforded and a damaged cylindrical guide for the drill string generally precludes the intended well from being drilled or requires significant effort to repair or replace it on the ocean floor.
Yet another feature of the present invention involves the placement of the drilling and foundation templates. The drilling template may be lowered and secured in place with piles, the docking pile guide frames attached in position, and the docking piles installed. When production becomes imminent, the foundation template may be set around the drilling template and the production platform secured thereto. This also allows the cost associated with the placement of the foundation template to be avoided, or at least delayed, until the delineation drilling has shown the field under development to have significant commercial potential.
Various other features, advantages and characteristics of the present invention will become apparent after a reading of the following description.